The present invention relates generally to the manufacture of automotive engine components possessing irregular exterior shapes using a powder metallurgy process, and more particularly to the manufacture of such components using a modified dynamic magnetic compaction (DMC) process with variably adjustable tooling.
Automotive engine camshaft lobes must endure significant and repeated mechanical loading under high-speed, high-temperature and tribologically-varying conditions. The use of conventional manufacturing processes, such as casting, forging or the like, tends to produce components which, while satisfactory from a load-bearing perspective, result in heavy, inefficient structures. Likewise, the use of such conventional manufacturing approaches is not conducive to tailoring a particular material's desirable properties to discreet locations on a camshaft lobe. Furthermore, the use of DMC, which is taught in U.S. Pat. Nos. 5,405,574, 5,611,139, 5,611,230 and 5,689,797 (all of which are hereby incorporated by reference), while a valuable way to compact both metallic and non-metallic powders to achieve high-density components, has not hitherto been extended to camshaft lobes, gears or other non-axisymmetric (i.e., non-cylindrical) or otherwise irregularly-shaped components.
Camshaft lobes are typically aligned such that they rotate about the common longitudinal axis of a shaft to which they are affixed, where the number of cam lobes varies depending on the configuration of the engine, including number of cylinders, valves per cylinder or the like. In fact, one notable attribute of a camshaft is the generally repeating nature of the various eccentricities and related protuberances along the length of the shaft. In recent years, cam lobes are also designed together in groups known as multi-lobe packs, in order to facilitate variable valve timing used for improved fuel efficiency, of which three-lobe packs are the most common. In these multi-lobe packs, rotational orientation of individual lobes may be staggered such that a protuberating portion of one lobe may be radially offset relative to that of its immediately axial neighboring lobe such that when the pack is coupled to a shaft and placed in an engine, the lobe orientation in the resulting camshaft ensures proper timing of engine valve opening and closing. Such offset configuration tends to exacerbate an already complicated arrangement of tooling used to make the lobe pack, where materials may additionally need to be strategically placed within the lobe to best take advantage of their particular structural properties in a lightweight, cost-effective way. It would be advantageous to develop ways to extend the efficient manufacturing attributes of DMC to the non-axisymmetric shapes of multi-component packs, such as camshaft lobe packs and related repeating-configuration components, to improve the quality and reduce the cost of producing the manufactured part.